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Windbreak Function (How do they work?) PowerPoint Presentation
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Windbreak Function (How do they work?)

Windbreak Function (How do they work?)

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Windbreak Function (How do they work?)

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  1. Windbreak Function(How do they work?) Joe Zeleznik NDSU Extension Forester

  2. Windbreak Function - Basics • They slow down the wind • They re-direct the wind • Which modifies the microclimate and environment in protected areas

  3. Based on Structure

  4. Based on Structure • Density - % solid

  5. Based on Structure • Density - % solid • Height – changes over time – height of tallest row

  6. Functional Height = Height of the tallest row

  7. Based on Structure • Density - % solid • Height – changes over time – height of tallest row • Length –

  8. PROTECTED AREA

  9. Based on Structure • Density - % solid • Height – changes over time – height of tallest row • Length – • Orientation – perpendicular to prevailing winds

  10. WIND

  11. From Northerly or northwesterly Direction 12 out of 24 From Southeasterly or Easterly Direction 10 out of 24 From Southwesterly Direction 2 out of 24

  12. Based on Structure • Density - % solid • Height – changes over time – height of tallest row • Length – • Orientation – perpendicular to prevailing winds • Continuity

  13. Based on Structure • Density - % solid • Height – changes over time – height of tallest row • Length – • Orientation – perpendicular to prevailing winds • Continuity • Species/Number of Rows

  14. How does structure affect wind speed and wind flow?

  15. Windspeed in the open Fastest Slowest Ground

  16. Windspeed in the open Fastest Slowest No turbulence over smooth ground Ground Turbulent flow over a rough surface

  17. Windspeed in the open Fastest Turbulent - Random Slowest No turbulence over smooth ground Ground Turbulent flow over a rough surface Eddy – Circular, against main flow

  18. Terms to know: H = height of object Upwind Windward Downwind Leeward

  19. Pressure eddy Solid barrier 1-2H

  20. Suction eddy Turbulent wake zone Resumption of open-field flow Solid barrier 1-3H 3-6H 6-8H

  21. Porous barrier Lower effect of pressure eddy

  22. Porous barrier Resumption of open-field flow Lower effect of suction eddy Turbulent wake farther downwind

  23. Lower branches pruned Resumption of open-field flow Increased snow spreading? Even lower effect of suction eddy Turbulent wake even farther downwind

  24. How does structure affect wind speed and wind flow? • Density – determines degree of wind speed reduction (and length of protected zone)

  25. Density Upwind Downwind

  26. How does structure affect wind speed and wind flow? • Density – determines degree of wind speed reduction (and length of protected zone) • Height – along with density, determines length of protected zone, upwind and downwind

  27. WIND HEIGHT Protected Area 2-5 H 10-20 H Protected Area Protected Area

  28. How does structure affect wind speed and wind flow? • Density – determines degree of wind speed reduction • Height – with density, determines length of protected zone, upwind and downwind • Length – determines total area of downwind protection

  29. LENGTH End effect: Windspeeds increased around end of windbreak by 1.1-1.3 times

  30. LENGTH

  31. PROTECTED AREA

  32. PROTECTED AREA Length:Height - > 10:1

  33. How does structure affect wind speed and wind flow? • Density – determines degree of wind speed reduction • Height – with density, determines length of protected zone, upwind and downwind • Length – determines total area of downwind protection • Orientation – place perpendicular to prevailing winds

  34. Wind ORIENTATION

  35. ? Wind

  36. ? PROTECTED AREA Wind

  37. Wind PROTECTED AREA ? PROTECTED AREA

  38. From Northerly or northwesterly Direction 12 out of 24 From Southeasterly or Easterly Direction 10 out of 24 From Southwesterly Direction 2 out of 24

  39. How does structure affect wind speed and wind flow? • Density – determines degree of wind speed reduction • Height – with density, determines length of protected zone, upwind and downwind • Length – determines total area of downwind protection • Orientation – place perpendicular to prevailing winds • Continuity

  40. CONTINUITY

  41. Brandle and Finch